Stimulation of resistance to Fasciola hepatica infection in sheep by a regime involving the use of the immunomodulatory compound L tetramisole (levamisole).

The effect of prior nematode and cestode infection in sheep on the course of experimental Fasciola hepatica was studied. The cross immunising properties of these parasites per se and the modification of any protective effect conferred by the immunomodulatory compound L tetramisole (levamisole) were investigated. It was recorded that no protection was conferred on sheep against F hepatica infection by virtue of prior infection with any helminth species per se, including Cysticercus tenuicollis. However, a degree of immunity to F hepatica was recorded, for only the second time, in sheep primed with helminth infections before treatment with levamisole. This is the first demonstration of a beneficial effect conferred by levamisole by virtue of its immunomodulatory properties in ruminants infected with any helminth species. Resistance was shown by a 47 per cent reduction in flukes recovered from sheep treated in this way (P less than 0.05).